A Pierce oscillator for MEMS resonant accelerometer with a novel low-power amplitude limiting technique

A low-power very compact Pierce oscillator for resonant accelerometers is presented in this paper. The resonator of a surface micro-machined uniaxial resonant accelerometer is embedded in the oscillating loop as a frequency selective filter. External accelerations cause a shift of the resonator resonance frequency resulting in the frequency modulation of the oscillator output signal. The proposed circuit exploits two sub-threshold operated FETs as the amplitude limiting control (ALC) network, capable of driving the resonator in its linear region of operation. The low power dissipation and the very compact 5 transistor (5T) architecture are the clear advantages of this oscillator. Experimental results demonstrate that the oscillation amplitude can be effectively limited to a desired value and that consumer grade performance can be achieved: an acceleration noise density of 360μg/VHz for a power dissipation of 21.6μW is demonstrated.